On Mar 31, 5:27=A0am, James A. Donald <jam...@[EMAIL PROTECTED]
> wrote:
> My take on it was that it was full of bunkum.
How much of that was the science or reference, and how much was the
unsubstantiated jump to "and thus plants are green"?
> It is evident that the system used by our green plants
> (green because they waste the dominant frequency) is an
> elaborate overly complicated and inefficient arrangement
> resulting from the accidents of history.
True, but some of those "inefficiencies" have been re-harnessed in
interesting ways as well (why I love learning about this stuff), such
as photorespiration. Yes, RuBisCO is lousy at the job it does, and is
very bad at selecting CO2 in the present atmosphere... but
photorespiration now also functions as a "safety valve" on the build-
up of a proton gradient to the point where it could damage the
membrane. There's no intent there, but on the other hand it's easy to
see how a system can get "locked in" to such inefficiencies. which,
again, is interesting.
> The theory explaining this that I find plausible is that
> the first photosynthesizers used hydrogen sulfide and
> absorbed green light. =A0The photosynthesizers at the
> bottom were short of green light, and short of hydrogen
> sulfide, so they used red light to synthesize a
> substitute for hydrogen sulfide, leading eventually to
> the two stage reaction used by today's green plants.
That does sound good, but it leads me to wonder what happened to the
green-light photosynthesizers. Maybe the two-stage mechanism produced
the ability to crack water, and thus opened up the world (literally)
to the descendants, but given the huge amount of energy thrown away by
reflecting green light, I'd expect some of those early organisms to
either have survived (as so many archea have) or to have been
incor****ated into the system (like the current photosystems in "higher
plants").
> It would therefore reflect light of low frequency and
> high frequency and absorb a broad band around the middle
> - thus would most likely look dark purple or dark red.
Probably.
--
Brian Davis
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